The man may soon feel the long arm of the law on his shoulder after the Y-fronts failed to stop him being picked up on CCTV.

Hilarious footage first shows a couple creeping down a staircase into the bar's cellar without a mask to steal two bottles of beer.

A minute later, a second man comes down wearing his undies on his head to take a whole 15 litre keg of lager.

The owner of the Gambrinus bar in the capital Minsk, Oliver Volkov, said: "My staff forgot to lock the door to the cellar as it was a busy night. I guess some of the guests noticed and decided to help themselves."

The bizarre video - now a comedy hit on YouTube - is being examined by local police who are hunting for the crook and his accomplices.

Police spokesman Darja Dashkevich said: "A waiter had forgotten to lock the cellar door and the thieves were taking advantage of that.

"We think someone out there must recognise the couple or the second man, despite his attempt to hide his face.

"The pants aren't such a good disguise because you can see everything through the leg holes and the Y-front."